How Long Will a Fogged Outboard Last in Storage?

This is the time of year that people start thinking about pulling their boats and winterizing them. Part of that routine is the so-called fogging of outboard engines, which is the process of injecting oil into the carburetor and cylinder(s) so that the engine won’t rust during storage, particularly if it is subject to wide temperature changes causing internal condensation. My question is, just how long is this storage technique good for?

Spraying fogging oil into the engine’s carb and cylinders prevents corrosion — but for how long?

Five years ago, I was in search of a small outboard engine. A friend, Ed, had a 5-hp Honda 4-stroke from the early 1990s that he was willing to sell because he had just bought a new, lighter 3-hp Mercury 2-stroke for his inflatable. The Honda wasn’t running. We didn’t know what was wrong, what it was worth, or how much it might cost to fix it, so before buying it I agreed to have it looked at by a certified Honda dealer–I took it to the Boat Guy Inc. on Cape Cod for evaluation.

It turns out the Honda ran beautifully after the rust was cleaned out of its fuel filter. However, the old metal external tank was scaling badly and needed replacing. I was told the engine was worth around $400, but it would need a new $180 tank and hose!

At that point, something surprising happened. The owner of the Boat Guy Inc., Andy Bancroft, an old acquaintance from my yacht yard operation days, approached me about buying the Honda outright. He explained that he collected old engines, that this was a missing piece to his collection, and said it would look dandy in his showroom lineup.

After telling him I really wanted an outboard kicker with a long shaft to push my project boat while I was searching for a replacement diesel, he smiled and said he had just the thing — a 2004 Mercury 6-hp 4-stroke long-shaft, replete with new tank and hose. It had been serviced, and was currently winterized and fogged out. I agreed to pay my buddy Ed $200 for his Honda (given that it would need a new tank) and then swapped it for the newer long-shaft Mercury. Everyone seemed happy with the deal.

Now the question comes. How long will a winterized, fogged-out engine last? You see, I got rid of the project boat after a tree limb damaged the mast last year, and I still have the Mercury in my nice warm basement. Truth be told, I have never run it, being reluctant to “unwinterize” it if I wasn’t ready to use it regularly. Oh, I’ve thought about selling it too, but I know I’ll need to demonstrate that it runs to any prospective buyer. I’ve got a barrel ready to test it in, and know I should satisfy myself that it runs. I have rolled it over a few times. I’m not sure who is more foggy on when to proceed — me on when to pull the starter handle, or the engine residing in a state of pure fogged-out stasis.

Eds’ note: If anyone out there has experience storing outboards over multiple seasons, tell us about it in the Comments section.